The present invention relates to a technology for contriving an enhancement of the performance of an optical system including beam deflection means, in a light scanning apparatus and an imaging apparatus (e.g., projector apparatus) for forming a two-dimensional image by use of a light modulation device having pixels arrayed in a one-dimensional form.
There have been known projector apparatuses for enlargingly projecting a two-dimensional image by use of a two-dimensional display device such as liquid crystal device, and, attendant on the introduction of a new broadcasting system, enhancement of image processing speed owing to the progress of computing devices, conversion from analog cinema to digital cinema and the like in recent years, there has been an increasing request for higher resolutions.
However, it is difficult for two-dimensional display devices to follow up to the enhancement of resolution. Specifically, in increasing the number of pixels, when it is contrived to obtain a higher resolution while fixing the size of the display device, it may be inevitable to reduce the openings in the display part, and it becomes difficult to realize a bright projector apparatus. On the other hand, when it is contrived to obtain a higher resolution while fixing the pixel size, it may be inevitable to increase the size of the display device, leading to an enlargement of the apparatus including an optical system and to a raised cost. Besides, in the manufacturing process of a two-dimensional display device, reduction of the pixels may need a countermeasure against mixing-in of smaller foreign matter; on the other hand, enlargement of the display device may need an enlargement of the production equipment.
There is known a system in which a light modulation device of a one-dimensional space modulation type is irradiated with a filamentous beam, and a one-dimensional image obtained by the light modulation device is projected onto a screen while scanning it along a direction orthogonal to the one-dimension direction by a light scanning means such as a galvanometer, thereby forming a two-dimensional image. Incidentally, in the one-dimensional space modulation type light modulation device, for example, a grating light valve (hereinafter referred to as “GLV”) developed by Silicon Light Machine (SLM) of USA, a plurality of movable ribbons are arrayed at a predetermined interval, and fixed ribbons are disposed between the adjacent movable ribbons. The movable ribbons are moved by impressing a drive voltage between a common electrode and the movable ribbons, to constitute a diffracting grating for the incident light.
For example, comparing a two-dimensional display device and a one-dimensional display device such as a GLV device while taking a high definition television (so-called HDTV) as an example, the two-dimensional display device may need 1920×1080, or about 2070 thousand pixels, whereas a system of scanning a one-dimensional image in a horizontal direction may need only 1080 devices; thus, there is a clear difference between both types of devices.
A GLV device is composed of a phase reflection type diffraction grating formed by the MEMS (MicroElectro Mechanical System) technology, and, where the GLV device is used with an illumination optical system for irradiating the device, the diffraction grating constituting each pixel is driven by a picture signal, and a phase difference generated thereby is controlled, whereby the function as an image display device is displayed. As a spatial filter for separating the ±1 order diffracted beams and the 0 order diffracted beam coming from each pixel from each other and shielding a specified light component (OFF light), the so-called schlieren optical system is adopted.
In relation to a projector optical system applied to a large-type display apparatus using one-dimensional display devices, there has been proposed, for example, a system in which a one-dimensional intermediate image is enlargedly projected by a projecting lens, and light scanning is conducted by use of a light deflector arranged at or around the pupil position of the projecting lens, to obtain a two-dimensional projected image on a screen (see, for example, Japanese Patent Application No. 2000-513114).
In addition, in application to a rear projector or the like, there may be mentioned a configuration in which a projecting lens system composed of a former group and a latter group is provided for shortening the projection distance, and a scan mirror is arranged in the air gap between the former group and the latter group (see, for example, Japanese Patent Laid-open No. 2002-131838).